In order to increase the bandwidth and communication speed of many computer and communication systems, optical fibers and optical components are increasingly being integrated into electronic systems. This integration typically involves conveying hundreds to thousands of optical signals between several substrates using optical fibers. FIG. 1 shows a cross-sectional view of a conventional coupler 1, which couples an optical fiber 4 to a channel waveguide 8 on a substrate 9. As shown in the figure, the end of the optical fiber is positioned to face the end of the channel waveguide. The core of the optic fiber typically has a circular cross-section, while the core of the channel waveguide typically has a square or rectangular cross-section.